From 3981b382fc655e5e209f6de5bfb3074769e476f1 Mon Sep 17 00:00:00 2001
From: Fabian Fichter <ianfab@users.noreply.github.com>
Date: Sun, 2 Sep 2018 15:10:24 +0200
Subject: [PATCH] Symmetrize evaluation for smaller board sizes

Piece-square tables remain asymmetrical.
---
 src/evaluate.cpp |   14 +++++++-------
 src/pawns.cpp    |   10 +++++-----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index a0d34be..971b44c 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -253,7 +253,7 @@ namespace {
     constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
     constexpr Direction Up   = (Us == WHITE ? NORTH : SOUTH);
     constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
-    constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
+    Bitboard LowRanks = rank_bb(relative_rank(Us, RANK_2, pos.max_rank())) | rank_bb(relative_rank(Us, RANK_3, pos.max_rank()));
 
     // Find our pawns that are blocked or on the first two ranks
     Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
@@ -272,7 +272,7 @@ namespace {
     if (pos.count<KING>(Us) && pos.non_pawn_material(Them) >= RookValueMg + KnightValueMg)
     {
         kingRing[Us] = attackedBy[Us][KING];
-        if (relative_rank(Us, pos.square<KING>(Us)) == RANK_1)
+        if (relative_rank(Us, pos.square<KING>(Us), pos.max_rank()) == RANK_1)
             kingRing[Us] |= shift<Up>(kingRing[Us]);
 
         if (file_of(pos.square<KING>(Us)) == FILE_H)
@@ -352,7 +352,7 @@ namespace {
                 score += Outpost[Pt == BISHOP][bool(attackedBy[Us][PAWN] & bb)];
 
             // Bonus when behind a pawn
-            if (    relative_rank(Us, s) < RANK_5
+            if (    relative_rank(Us, s, pos.max_rank()) < RANK_5
                 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
                 score += MinorBehindPawn;
 
@@ -388,7 +388,7 @@ namespace {
         if (Pt == ROOK)
         {
             // Bonus for aligning rook with enemy pawns on the same rank/file
-            if (relative_rank(Us, s) >= RANK_5)
+            if (relative_rank(Us, s, pos.max_rank()) >= RANK_5)
                 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[Us][ROOK][s]);
 
             // Bonus for rook on an open or semi-open file
@@ -575,7 +575,7 @@ namespace {
             Square s = pop_lsb(&b);
             score += ThreatByMinor[type_of(pos.piece_on(s))];
             if (type_of(pos.piece_on(s)) != PAWN)
-                score += ThreatByRank * (int)relative_rank(Them, s);
+                score += ThreatByRank * (int)relative_rank(Them, s, pos.max_rank());
         }
 
         b = (pos.pieces(Them, QUEEN) | weak) & attackedBy[Us][ROOK];
@@ -584,7 +584,7 @@ namespace {
             Square s = pop_lsb(&b);
             score += ThreatByRook[type_of(pos.piece_on(s))];
             if (type_of(pos.piece_on(s)) != PAWN)
-                score += ThreatByRank * (int)relative_rank(Them, s);
+                score += ThreatByRank * (int)relative_rank(Them, s, pos.max_rank());
         }
 
         b = weak & attackedBy[Us][KING];
@@ -679,7 +679,7 @@ namespace {
         bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
         score -= HinderPassedPawn * popcount(bb);
 
-        int r = relative_rank(Us, s);
+        int r = relative_rank(Us, s, pos.max_rank());
         int w = PassedDanger[r];
 
         Score bonus = PassedRank[r];
diff --git a/src/pawns.cpp b/src/pawns.cpp
index 78f395b..5c1e8b1 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -124,7 +124,7 @@ namespace {
             e->passedPawns[Us] |= s;
 
         else if (   stoppers == SquareBB[s + Up]
-                 && relative_rank(Us, s) >= RANK_5)
+                 && relative_rank(Us, s, pos.max_rank()) >= RANK_5)
         {
             b = shift<Up>(supported) & ~theirPawns;
             while (b)
@@ -134,7 +134,7 @@ namespace {
 
         // Score this pawn
         if (supported | phalanx)
-            score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
+            score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s, pos.max_rank())];
 
         else if (!neighbours)
             score -= Isolated, e->weakUnopposed[Us] += !opposed;
@@ -206,7 +206,7 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
 
   constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
   constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
-  constexpr Bitboard  BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
+  Bitboard  BlockRanks = rank_bb(relative_rank(Us, RANK_1, pos.max_rank())) | rank_bb(relative_rank(Us, RANK_2, pos.max_rank()));
 
   Bitboard b = pos.pieces(PAWN) & (forward_ranks_bb(Us, ksq) | rank_bb(ksq));
   Bitboard ourPawns = b & pos.pieces(Us);
@@ -221,10 +221,10 @@ Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
   for (File f = File(center - 1); f <= File(center + 1); ++f)
   {
       b = ourPawns & file_bb(f);
-      int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
+      int ourRank = b ? relative_rank(Us, backmost_sq(Us, b), pos.max_rank()) : 0;
 
       b = theirPawns & file_bb(f);
-      int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
+      int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b), pos.max_rank()) : 0;
 
       int d = std::min(f, ~f);
       safety += ShelterStrength[d][ourRank];
-- 
1.7.0.4